Rapid transmission of the protozoan parasite Histomonas meleagridis in turkeys and specific pathogen free chickens following cloacal infection with a mono-eukaryotic culture.

In the present investigation, the pathogenicity and transmission of a mono-eukaryotic culture of Histomonas meleagridis for commercial turkeys and specific pathogen free (SPF) chickens is described for the first time. Two separate trials with the same kind of experimental design were performed, one with commercial turkeys and one with SPF chickens. In each experiment, two different groups were included, which were housed in separate rooms. The first group contained four control birds, whereas the second group consisted of 10 infected and four in-contact birds. The birds were infected via the cloaca at 14 days of age with 380,000 cells of a mono-eukaryotic culture of H. meleagridis consisting of a cloned isolate (Turkey/Austria/2922-66/04). Reisolation of the parasite from turkeys and chickens under experimental conditions was performed for the first time. The infected birds started to excrete the parasite as soon as 2 days post infection. Rapid spread of the parasite to in-contact turkeys and chickens was noticed, based on reisolation of live parasites. Reisolation of the pathogen was impossible from two of the four in-contact SPF chickens at any time, whereas all of the infected turkeys were found positive. Intermittent shedding of the parasite was noticed in infected turkeys and SPF chickens, but the phenomenon was much more severe in the SPF chickens as these birds survived the infection. All of the infected and in-contact turkeys died between days 11 and 14 post infection, whereas no death was recorded in the SPF chickens, which were killed 6 weeks after the infection. Typical lesions were recorded in the caeca and livers of the infected turkeys. In addition, a heavy destruction of the bursa of Fabricius was seen in all of the infected and one of the in-contact turkeys. Altogether, the present investigations are of importance for an understanding of the pathogenicity and transmission of H. meleagridis in poultry.     

Significance of paroviruses, entero-like viruses and reoviruses in the aetiology of the chicken malabsorption syndrome

Specific-pathogen-free White Leghorn chickens and commercial broilers were inoculated orally at 1 day of age with different intestinal preparations containing a chicken parvovirus, an entero-like virus associated with a reovirus from field materials, or the entero-like viruses and reovirus alone. Despite viral multiplication in inoculated birds, no clinical signs or growth retardation were observed in SPF and broiler chickens infected with the reo or parvo viruses. Abnormal faeces and reduction in weight gains were observed after infection with the field materials and the entero-like viruses. Some easily sedimentable particles could be involved with the entero-like virus in the aetiology of ranting syndrome. Proventriculitis was present in chickens inoculated with one of the field materials and with the entero-like virus isolated from that material. Specific-pathogen-free White Leghorn chickens were as susceptible as commercial broiler chickens to weight gain depression after oral inoculation with crude homogenates at 1 day of age.     

Detection of antibody to chicken anaemia agent: a comparison of three serological tests

A comparison was made between sensitivities of the virus neutralisation (VN) test, indirect fluorescent-antibody (IFA) test and enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to chicken anaemia agent (CAA). Sera from chickens inoculated with CAA at 11 weeks of age and from specific pathogen-free (SPF) and field breeder chicken flocks were tested. Seroconversion was detected by the three tests in all the inoculated birds at 2 to 3 weeks post-inoculation (pi). Neutralising antibody to CAA was still detectable in all the inoculated birds 37 weeks after infection, the end of the observation period. One of the seven inoculated birds tested by the ELISA gave positive results for the same period whereas the IFA test detected anti-CAA antibody only for 9 weeks. In field sera, the VN test detected many more positive sera than did the ELISA and IFA test. No antibodies to CAA were detected in sera of SPF chickens by the three tests. The IFA test frequently gave false positive results when VN antibody-negative sera were tested at dilutions of 相似文献   

Comparison of the replication and transmissibility of two infectious laryngotracheitis virus chicken embryo origin vaccines delivered via drinking water

Infectious laryngotracheitis (ILT) is an acute infectious viral disease that affects chickens, causing respiratory disease, loss of production and mortality in severe cases. Biosecurity measures and administration of attenuated viral vaccine strains are commonly used to prevent ILT. It is notable that most recent ILT outbreaks affecting the intensive poultry industry have been caused by vaccine-related virus strains. The purpose of this study was to characterize and compare viral replication and transmission patterns of two attenuated chicken embryo origin ILT vaccines delivered via the drinking water. Two groups of specific pathogen free chickens were each inoculated with SA-2 ILT or Serva ILT vaccine strains. Unvaccinated birds were then placed in contact with vaccinated birds at regular intervals. Tracheal swabs were collected every 4 days over a period of 60 days and examined for the presence and amount of virus using a quantitative polymerase chain reaction. A rapid increase in viral genome copy numbers was observed shortly after inoculation with SA-2 ILT virus. In contrast, a comparatively delayed virus replication was observed after vaccination with Serva ILT virus. Transmission to in-contact birds occurred soon after exposure to Serva ILT virus but only several days after exposure to SA-2 ILT virus. Results from this study demonstrate in vivo differences between ILT vaccine strains in virus replication and transmission patterns.     

Experimental infection of chickens with an australian strain of reticuloendotheliosis virus. I. Clinical, pathological and haematological effects

A wide range of clinical, pathological and haematological effects were found over a 40-week period in chickens inoculated at 1-day-old with a low-passage, cell-culture preparation of an Australian strain of reticuloendotheliosis virus. Feathering defects and statistically significant depression of body weights occurred in chickens up to 8 weeks of age. Other findings in birds that died or were culled during the 40-week experimental period included mild anaemia, leucopenia, heterophilia, hypoplasia of immune system organs, inflammation in visceral and nervous system organs, and bacterial or fungal infections. These results suggested that ill-thrift and death in some chickens infected with reticuloendotheliosis virus may be due to secondary infections with microorganisms subsequent to damage of immune system organs by that virus. Lymphoreticular-cell tumours of the liver, kidney or spleen were found in two birds aged 22 and 24 weeks. These results establish reticuloendotheliosis virus as a possible cause of tumours in adult fowls. Horizontal transmission of virus was demonstrated but the only abnormalities detected in the in-contact chickens were feathering defects.     

The activity in the chicken alimentary tract of bacteriophages lytic for Salmonella typhimurium

Bacteriophages lytic for Salmonella typhimurium were isolated in considerable numbers from chickens experimentally infected with S. typhimurium, and in much lower numbers from the chicken feed. Lytic phages were also regularly isolated from human sewerage systems. One of these was used to inoculate S. typhimurium--infected two day-old chickens orally and via the feed. The phage took longer to establish in the caeca than did the Salmonella and it disappeared when the caecal S. typhimurium counts fell to 10(6) CFU/ml. No neutralizing antibodies to the phage were detected in the serum of these chickens. In a second experiment, five of 30 chickens similarly infected with S. typhimurium were inoculated with the phage. Within 3 days, the phage was isolated from 72% of the "in-contact" birds. A second phage, isolated from sewage, when inoculated into newly-hatched chickens simultaneously with any of 3 strains of S. typhimurium, produced a considerable reduction in mortality in the birds. This effect was only produced by inoculation of high concentrations of phage (greater than 10(10) PFU/ml). The phage produced reductions in the viable numbers of S. typhimurium in the crop, small intestine and caeca for up to 12 h after inoculation, with smaller reductions in bacterial numbers in the liver at 24 and 48 h after infection.     

Effect of vaccination on transmission characteristics of highly virulent Newcastle disease virus in experimentally infected chickens

An experimental study was conducted to evaluate the effect of vaccines produced in Ethiopia from vaccine strains used worldwide on the transmission characteristics of velogenic Newcastle disease virus field strain after different vaccination schemes. Chickens were vaccinated with Hitchner B1, La Sota or I-2 via the intraocular and intranasal routes. Vaccine and challenge viruses induced high antibody levels, both in inoculated and contact birds. Prime-boost vaccination protected birds against morbidity and mortality and significantly reduced the incidence of viral shedding from chickens compared with single vaccinated and unvaccinated birds. Protection from disease and mortality was correlated with the presence of positive antibody titres (>4 log₂) at day of challenge. Most of the unvaccinated and in-contact birds excreted the virus and showed a high level of antibody titres, indicating the high infectivity of the challenge virus. The detection of the challenge virus in most of vaccinated birds demonstrated that the tested vaccination protocols cannot fully protect birds from viral infection, replication and shedding, and vaccinated–infected birds can act as a source of infection for susceptible flocks. The high mortality observed in unvaccinated birds and their contacts confirmed the virulence of the challenge virus and indicated that this field virus strain can easily spread in an unvaccinated poultry population and cause major outbreaks. Progressive vaccinations supported by biosecurity measures should therefore be implemented to control the disease and introduction of the virus to the poultry farms.     

Experimental infection of chickens with an Australian strain of reticuloendotheliosis virus. 2. Serological responses and pathogenesis

Fifteen SPF chickens were inoculated with an Australian strain of reticuloendotheliosis virus (REV) at 1 day of age and five uninoculated chickens were readily infected by horizontal spread from this group. Antibody detectable by the immunofluorescent antibody (IFA) test developed 3 to 6 weeks after infection, and usually persisted for 20-35 weeks, with maximum titres (40-1280) at 8 to 13 weeks. Agar gel precipitin (AGP) reactions developed more slowly and were variable in duration, the highest proportion of positive reactions being detectable 8 to 13 weeks after infection and persisting for 8 to 30 weeks. Infectious REV was readily detected in the plasma and serum of inoculated chickens 6 weeks after infection and a non-infectious REV antigenaemia usually persisted for at least a further 7 weeks, in the presence or absence of antibody. Development of a detectable REV viraemia was strongly associated with poor body development and premature mortality among the inoculated chickens. In two inoculated chickens which failed to develop detectable serological reactions, a REV viraemia occurred which persisted throughout life. At autopsy, REV was re-isolated from the kidneys of most of the inoculated chickens and from the reproductive and intestinal systems of two birds 22 and 56 weeks after infection.     

Big liver and spleen disease of broiler breeders

Five adult broiler breeders were inoculated with faeces and tissue extracts from birds with big liver and spleen (BLS) disease. Five birds were placed in contact with the inoculated birds. After 8 weeks all inoculated and four of the five in-contact birds were shown to be infected as evidenced by the detection of an immune response and/or the demonstration of BLS antigen in spleen and tissue smears, by an immunofluorescence test and by agar gel immunodiffusion. Using appropriate antisera BLS antigen was found mainly in phagocytic liver cells and in splenic macrophages and dendritic cells. Fewer cells containing antigen were found in the kidney. Double staining of liver and spleen tissue for BLS antigen and chicken immunoglobulin indicated that many cells were positive for both. It is possible that BLS antigen in most cells may represent phagocytosed material rather than a replicating agent. If so, while this could explain the failure to detect virus-like particles, it implies that the primary site of replication of the BLS agent and its nature remain to be established.     

Evaluation of the protection elicited by direct and indirect exposure to live attenuated infectious laryngotracheitis virus vaccines against a recent challenge strain from the United States

In a recent study (Oldoni & García, 2007), some field strains of infectious laryngotracheitis viruses (ILTV) were characterized as genotypically different (group VI) from ILT vaccine strains. The objective of this study was to evaluate the protection elicited by one chicken embryo origin (CEO) and one tissue culture origin (TCO) vaccine against a field isolate from group VI after direct and indirect exposure to ILTV live attenuated vaccines. In phase 1 of the experiment, non-vaccinated chickens were placed into contact with the eye drop vaccinates for a period of four weeks after vaccination. Transmission of the vaccine virus to these in-contact birds was demonstrated by real time PCR and antibody production, although the in-contact birds did not become protected against disease when subsequently challenged in phase 2 of the experiment. This emphasized the importance of uniform vaccination to obtain adequate protection, both to avoid the occurrence of susceptible chickens, and to minimize the potential for reversion to virulence of live-attenuated vaccines. In phase 2, protection against challenge with a group VI field virus was assessed four weeks after vaccination by scoring clinical signs and mortality, and quantifying weight gain. Sentinel birds were added to the groups one day after challenge to assess shedding of challenge virus, using real time PCR and virus isolation, during the period 2 to 12 days post challenge. The results showed that the CEO and TCO eye drop-vaccinated chickens were protected against challenge with the group VI virus, even though it was genetically different from the vaccine strains, and that challenge virus was not transmitted from these protected birds to the sentinels.     

Studies on experimental tenosynovitis in light hybrid chickens

A group of light hybrid chicks was inoculated via the footpad at 1-day-old with an avian reovirus isolated from ruptured gastrocnemius tendons, and were housed with a similar number of uninoculated chicks (in-contacts) from the same hatch. Though all inoculated birds showed swellings of the injected leg after 7 days, lesions of tenosynovitis did not develop in the other leg or in either leg of in-contacts until they were 6- to 7-weeks-old. Lesions in leg tendons, and particularly the digital flexors, persisted in both inoculated and in-contact birds until the termination of the experiment at 33 weeks of age. Reovirus was recovered for varying periods from the trachea, intestine, hock and footpad of inoculated chickens commencing 1 week after infection, and from the same tissues of in-contacts but from 2 weeks, and generally for shorter periods. In both groups virus persisted for at least 13 weeks in the hock joint or surrounding tissues and cloacal swabs were positive between the 14th and 16th weeks after inoculation. Fluorescent antibody staining demonstrated penetration of the virus into the tendons. Precipitating antibodies to the reovirus were detectable in both groups between the 3rd and 24th weeks after infection.     

The effect of a live vaccine on the horizontal transmission of Mycoplasma gallisepticum.

The effect of a live Mycoplasma gallisepticum vaccine on the horizontal transmission of this Mycoplasma species was quantified in an experimental animal transmission model in specific pathogen free White Layers. Two identical trials were performed, each consisting of two experimental groups and one control group. The experimental groups each consisted of 20 birds 21 weeks of age, which were housed following a pair-wise design. One group was vaccinated twice with a commercially available live attenuated M. gallisepticum vaccine, while the other group was not vaccinated. Each pair of the experimental group consisted of a challenged chicken (10(4) colony-forming units intratracheally) and a susceptible in-contact bird. The control group consisted of 10 twice-vaccinated birds housed in pairs and five individually housed non-vaccinated birds. The infection was monitored by serology, culture and quantitative polymerase chain reaction. The vaccine strain and the challenge strain were distinguished by a specific polymerase chain reaction and by random amplified polymorphic DNA analysis. In both experiments, all non-vaccinated challenged chickens and their in-contact 'partners' became infected with M. gallisepticum. In the vaccinated challenged and corresponding in-contact birds, a total of 19 and 13 chickens, respectively, became infected with M. gallisepticum. Analysis of the M. gallisepticum shedding patterns showed a significant effect of vaccination on the shedding levels of the vaccinated in-contact chickens. Moreover, the Cox Proportional Hazard analysis indicated that the rate of M. gallisepticum transmission from challenged to in-contact birds in the vaccinated group was 0.356 times that of the non-vaccinated group. In addition, the overall estimate of R (the average number of secondary cases infected by one typical infectious case) of the vaccinated group (R = 4.3, 95% confidence interval = 1.6 to 49.9) was significantly lower than that of the non-vaccinated group (R = infinity, 95% confidence interval = 9.9 to infinity). However, the overall estimate of R in the vaccinated group still exceeded 1, which indicates that the effect of the vaccination on the horizontal transmission M. gallisepticum is insufficient to stop its spread under these experimental conditions.     

Experimental infection of chickens with an adenovirus isolated from tenosynovitis, following infection with either (1) an arthrotropic reovirus, or (2) infectious bursal disease virus

In an attempt to show arthrotropic activity for an adenovirus isolated from tenosynovitis in chickens, but which did not cause tenosynovitis on its own, two dual infections were conducted. In the first, specific pathogen-free (SPF) chicks were infected with a tenosynovitis-inducing reovirus at 1-day-old, and the adenovirus was given 3 days later. In both cases viruses were administered orally or via the footpad. The adenovirus did not exacerbate reovirus-induced lesions of tenosynovitis. There was an indication that lesions regressed more rapidly in dually-infected chickens. Neither virus appeared to influence the persistence of the other in joints or the gut. In a second experiment, infectious bursal disease virus (IBDV) was inoculated onto the conjunctiva of 1-day-old SPF chicks and 6 days later they were infected with the adenovirus by either route. No tenosynovitis occurred, although preinfection with IBDV caused a more prolonged shedding of adenovirus, and in a greater proportion of the birds than those infected with adenovirus alone. In neither experiment did the dual infection cause the adenovirus to become pathogenic for the hock joints. It is considered that there is no evidence that adenoviruses are important agents of hock disorders in the chicken.     

A unique isolate of beak and feather disease virus isolated from budgerigars (Melopsittacus undulatus) in South Africa

Beak and feather disease virus (BFDV), the causative agent of psittacine beak and feather disease (PBFD) infects psittaciformes worldwide. We provide an annotated sequence record of three full-length unique genomes of BFDV isolates from budgerigars (Melopsittacus undulatus) from a breeding farm in South Africa. The isolates share >99% nucleotide sequence identity with each other and ~96% nucleotide sequence identity to two recent isolates (Melopsittacus undulatus) from Thailand but only between 91.6 and 86.6% identity with all other full-length BFDV sequences. Maximum-likelihood analysis and recombination analysis suggest that the South African budgerigar BFDV isolates are unique to budgerigars, are non-recombinant in origin, and represent a new genotype of BFDV.     

Isolation of highly cytolytic MDV strains from Germany and Spain.

Four serotype 1 Marek's disease virus (MDV) strains were isolated from Marek's disease (MD) outbreaks in Germany and Spain and their virulence was tested in SPF White Leghorn chickens. Two of the isolates from Germany (MR48/1-2 and /2-8) induced early mortality from cytolytic MD in 25% of the chickens whereas one isolate from Germany (MR48/3-16) caused early mortality in 58% of the inoculated chickens. Histological examination showed severe depletion of the lymphoid tissue of the bursa of Fabricius and the thymus, consistent with the cytolytic phase of MD. AH surviving chickens later developed acute MD in the form of multiple visceral tumours. Inoculation of SPF chickens with various doses of the isolate MR36 8/1C (Spain) caused early mortality in up to 69% of the chickens and acute MD in 92 to 100% of the chickens surviving the cytolytic phase of the disease.     

Avian retrovirus infection causes naturally occurring glioma: Isolation and transmission of a virus from so-called fowl glioma

So-called fowl glioma is characterized by multiple nodular gliomatous growths associated with disseminated non-suppurative encephalitis. To investigate the possibility of the induction of the gliomatous lesions, chicks of Japanese bantams ( Gallus gallus domesticus ) and specific pathogen free chickens (C/O strain White Leghorn) were intracerebrally inoculated with a brain homogenate or culture supernatant from a bantam affected with fowl glioma. All bantams and 16 chickens (89%) in the inoculated groups showed non-suppurative encephalitis, and the 18 bantams (82%) and five chickens (28%) developed multiple nodules consisting of aggregations of astrocytes in the cerebrum. These astrocytes had avian leukosis virus (ALV) antigen. By Southern blot analysis, the ALV sequence was detected both in DNA prepared from the brains of the inoculated birds and in DNA from the inoculum. Ultrastructurally, tadpole-shaped particles, approximately 100 nm in diameter, were detected in the concentrated supernatant of the chicken embryo fibroblasts, and budding of the particles was noted. These results substantiated that fowl glioma of the bantams could be transmitted by intracerebral inoculation of the affected tissue and that the causal agent was an unidentified strain of ALV.     

Generation and infectivity titration of an infectious stock of avian hepatitis E virus (HEV) in chickens and cross-species infection of turkeys with avian HEV

Avian hepatitis E virus (HEV), a novel virus identified from chickens with hepatitis-splenomegaly syndrome in the United States, is genetically and antigenically related to human HEV. In order to further characterize avian HEV, an infectious viral stock with a known infectious titer must be generated, as HEV cannot be propagated in vitro. Bile and feces collected from specific-pathogen-free (SPF) chickens experimentally infected with avian HEV were used to prepare an avian HEV infectious stock as a 10% suspension of positive fecal and bile samples in phosphate-buffered saline. The infectivity titer of this infectious stock was determined by inoculating 1-week-old SPF chickens intravenously with 200 microl of each of serial 10-fold dilutions (10(-2) to 10(-6)) of the avian HEV stock (two chickens were inoculated with each dilution). All chickens inoculated with the 10(-2) to 10(-4) dilutions of the infectious stock and one of the two chickens inoculated with the 10(-5) dilution, but neither of the chickens inoculated with the 10(-6) dilution, became seropositive for anti-avian HEV antibody at 4 weeks postinoculation (wpi). Two serologically negative contact control chickens housed together with chickens inoculated with the 10(-2) dilution also seroconverted at 8 wpi. Viremia and shedding of virus in feces were variable in chickens inoculated with the 10(-2) to 10(-5) dilutions but were not detectable in those inoculated with the 10(-6) dilution. The infectivity titer of the infectious avian HEV stock was determined to be 5 x 10(5) 50% chicken infectious doses (CID(50)) per ml. Eight 1-week-old turkeys were intravenously inoculated with 10(5) CID(50) of avian HEV, and another group of nine turkeys were not inoculated and were used as controls. The inoculated turkeys seroconverted at 4 to 8 wpi. In the inoculated turkeys, viremia was detected at 2 to 6 wpi and shedding of virus in feces was detected at 4 to 7 wpi. A serologically negative contact control turkey housed together with the inoculated ones also became infected through direct contact. This is the first demonstration of cross-species infection by avian HEV.     

Induction of lymphomas by inoculation of Marek's disease virus-derived lymphoblastoid cell lines: prevention by CVI988 vaccination

Lymphoblastoid cell lines 265(L) and 990(O) are monoclonal lymphomas, derived respectively from liver and ovarian tumours, generated in inbred P-line (MHC B¹⁹/B¹⁹) chickens infected with RB-1B strain of Marek's disease virus (MDV) and pRB-1B5 BAC clone respectively. These were inoculated into inbred, MDV-susceptible, P-line chickens by intra-venous or intra-abdominal routes. Additional groups of birds were vaccinated using 1000 plaque-forming units of CVI988 vaccine 8 days prior to inoculation of the cell lines. Non-vaccinated birds developed visceral Marek's disease tumours with an increased rate 30 to 60 days post inoculation. Vaccination prevented tumour and disease development in challenged birds. TCRβ repertoire analysis by spectratyping and sequencing of the inoculum was used to track tumour identity in primary tumours and tumour cell lines derived from inoculated birds. These data revealed that the tumours were a consequence of de novo virus infection and not metastasis and expansion of the inoculated tumour cells. Moreover, the data showed that the two MDV-derived cell lines were not transplantable even in syngeneic P-line birds. The data also demonstrated the application of spectratyping as a tool to track tumour identity in lymphoma transplantation studies.     

Efficacy and safety of an attenuated live QX-like infectious bronchitis virus strain as a vaccine for chickens

The attenuation of infectious bronchitis (IB) QX-like virus strain L1148 is described. The virus was passaged multiple times in embryonated specific pathogen free (SPF) chicken eggs, and at different passage levels samples were tested for safety for the respiratory tract and kidneys in 1-day-old SPF chickens. There was a clear decrease in pathogenicity for the respiratory tract and kidneys when the virus had undergone a large number of passages. Passage level 80 was investigated for safety for the reproductive tract in 1-day-old and 7-day-old SPF chickens. In 1-day-old chickens, 12.5% of the vaccinated birds had macroscopic lesions. No lesions were observed if the chickens had been vaccinated at 7 days of age. Passage level 80 was investigated for its ability to spread from vaccinated to non-vaccinated chickens and for dissemination in the body. The virus was able to spread from vaccinated chickens to groups of non-vaccinated chickens, and in the vaccinated birds the virus was found frequently in oro-pharyngeal and cloacal swabs. A fragment of the hypervariable region of the S1 protein of passage level 80 was sequenced and revealed nucleotide changes resulting in two amino acid substitutions. Passage level 80 was given additional passages to levels 82 and 85. Both passage levels were tested for efficacy in SPF chickens and passage level 85 was tested for efficacy in commercial chickens with maternally derived antibodies (MDA) against a challenge with QX-like strain IB D388. In both SPF chickens and chickens with MDA, the vaccines based on strain IB L1148 were efficacious against challenge.